Generally, the waste printed circuit boards contain noble metals such as gold and silver, and valuable metals such as iron, copper, and nickel.
As changes in performance and profile of the electronic machine rapidly proceed according to needs of consumers, usage duration of the electronic machines is becoming shortened. Subsequently, the amount of the waste printed circuit boards generated is being increased. The producers have the increased burden of processing the waste electronic machine, and also environmental contamination due to the waste electronic machine causes a social problem. Since the waste printed circuit board contains a large amount of valuable metals, the valuable metals can be recovered via proper processes to allow it to be reused, which is very useful in term of resource utilization and prevention of environmental contamination.
In order to recover the valuable metal from the waste printed circuit boards, it is necessary to remove the non-metal component which occupies about 40˜60% of the waste printed circuit boards. The process of separating the metal components and the plastic components from the waste printed circuit boards is broadly divided into a physical separation process and a wet process.
As a conventional technology, Korean Patent laid-open No. 2003-0006792 relates to a method for recovering the valuable metal from the waste printed circuit boards, in which there is disclosed a technology of passing the waste printed circuit boards through crushing, air separation, electrostatic separation and magnetic separation process, and then melting and separating copper, iron, zinc, nickel and aluminum components using sulfuric acid and oxygenated water, melting and separating gold and silver using (NH4)2S2O3, CuSO4, and NH4OH solution, melting and separating lead using salt water, and melting and separating palladium using sulfuric water.
Further, Korean Patent laid-open No. 1999-0070807 relates to a method of extracting the noble metals from the waste printed circuit boards using converter and electric furnace slag, in which there is disclosed a technology for extracting the noble element such as gold, silver, platinum family element from the waste printed circuit boards.
Korean Patent Laid-Open No. 1998-068762 relates to a method of recovering the valuable metals from the waste printed circuit boards, in which there is disclosed a technology of recovering the valuable metals from the waste printed circuit boards by the physical separation process using an inclined vibration plate after being crashed by a hammer mill.
Korean Patent Laid-Open No. 2001-0067641 relates to a method of recovering the valuable metal element from the waste printed circuit boards using Chelate resin, and discloses a technology for recovering the noble metal element by crashing the waste printed circuit boards, melting the metal component to cause it to be absorbed into the Chelate resin, and desorpting the valuable metal absorbed into the Chelate resin using an eluant.
Korean Patent Laid-Open No. 2007-0077114 discloses a technology for recovering tin using heat melting and tin removal solution, melting and separating copper using strong acid solution, separating brominates epoxy resin from glass fiber by heat chemical reaction using Sodium Nitrate, and recovering carbonized glass fiber and copper lamina using water cleaning.
Japanese Patent Laid-Open No. 2005-324176 relates to a method for recycling the waste printed circuit boards, in which there is disclosed a technology for recovering metal materials and insulated materials using a forced filtering method applying pressure after making viscosity of thermoplastic resin lower by heating the waste printed circuit boards produced by the thermoplastic resin.
U.S. Pat. No. 5,979,033 relates to a method for recycling the waste printed circuit boards, and discloses a technology for recovering sheet copper, thermosetting resin and glass fiber by crashing the waste printed circuit boards, putting it into melted tin, and then stirring and carbonizing it.
In a case of using the wet process such as the Korean Patent Laid-Open No. 2003-0006792, the Korean Patent Laid-Open No. 2001-0067641, the U.S. Pat. No. 5,979,033, since the metal components are recovered by leaching it from the waste printed circuit boards using acid, there are disadvantages that the criterion for determining the leaching rate must be dependent upon experience and waste water is excessively generated, which result in difficulty in commercialization.
Meanwhile, in a case of using the physical separation process such as the Korean Patent Laid-Open No. 1998-068762 and the Japanese Patent Laid-Open No. 2005-324176, though it is preferable that the procedure is simple and the waste water is not generated, the separation efficiency upon separating the metal component and the non-metal component from the waste printed circuit boards using the physical separation method is disadvantageously lowered. As well, the metal components present between the plastic components can not be substantially recovered, and therefore loss ratio of the metal components is disadvantageously increased.